Article Date: 10/1/2000

1000022

Orthokeratology Overview

Roger L. Tabb, O.D., F.A.A.O., F.I.O.S.
October 2000

An alternative to refractive surgery, the non-permanent ortho-k procedure involves wearing special design lenses.

People have attempted to correct refractive error for a long time. Hundreds of years ago, the Chinese laid sandbags on closed eyelids, creating pressure to flatten the cornea to improve unaided visual acuity. More recently, a device was invented and marketed in 1905 by a mail order catalogue, claiming to improve near- sightedness. It was a spring-loaded device which, when held against the closed eye and triggered, would produce a thump on the cornea, causing the cornea to flatten temporarily, supposedly improving unaided visual acuity (and probably causing a sharp spike in IOP). Great strides have been made since those times.

Modern Orthokeratology

Orthokeratology has existed since the 1960s. It is a non-invasive procedure in which contact lenses change the shape of the cornea to reduce refractive error. Since its advent, orthokeratology has experienced variable results. Some of the lens designs used initially produced unpredictable and fleeting changes. Opponents immediately claimed ortho-k was not permanent, predictable or effective. Most successful reports were anecdotal, and the scientific community understandably claimed to need more scientific studies. Until recently, industry, professional organizations and other professionals have offered little support. This increased interest has largely been due to the advent of well-designed reverse geometry lenses.

Proponents of orthokeratology will emphasize that the changes in refraction today are more predictable and long lasting due to improvements in lens designs. Lenses can effect change without weakening the cornea. The lack of permanency is actually an advantage. Ortho-k has a high safety record because it is almost always reversible. Patients such as pilots, police officers and fire fighters not desiring refractive surgery can now meet unaided visual acuity levels.

Ortho-k lenses fall into two categories: daywear and nightwear. Daywear consists of wearing a specially- designed lens (spherical, aspherical or complex reverse geometry) under daytime conditions to improve unaided visual acuity when the lenses are removed. This improved unaided vision will generally last fewer hours than that created by nightwear lenses. Daywear lenses have been available for 40 years and have been successful to varying degrees.

Nightwear involves wearing a reverse geometry lens while sleeping to allow unaided vision during waking hours. This procedure is not yet FDA approved. These specific designs can truly be referred to as a mold because they create a living visco-elastic mold for the cornea. I believe properly-designed nightwear orthokeratology lenses produce a more accurate, rapid, safe and lasting unaided visual acuity result than daywear lenses.

Daywear Ortho-k

Advantages of Daywear

Disadvantages of Daywear

Nightwear Ortho-k

Advantages of Nightwear

Disadvantages of Nightwear

12-year old male student/athlete
Beginning: OD: ­1.50­4.00 x 013 OS:­2.00­3.75 x 163
1 Day: OD: +0.50 OS: Pl­2.25 x 163 20/25­1 OU
7 Month: OD: Plano OS: ­1.00 20/20+3 OU

 

40-year old female secretary/receptionist
Beginning: OD: ­3.00 OS: ­3.25 20/400 OU
1 Day: OD: ­2.00 OS: ­1.50 20/50, 20/70
1 Month: OD: Plano OS: Plano 20/15 OU

Dr. Tabb is in private group practice in Portland, Ore., and has been involved in ortho-k for the past 34 years. He is president of the consulting company Advanced Corneal Engineering and has a patent pending on his NightMove ortho-k lens design.


Contact Lens Spectrum, Issue: October 2000